Minimally invasive surgery is a surgical approach aimed at intervening inside the body of a patient by accessing organs on which intervention must be made, by making a minimum number of openings in the body. For this purpose, the surgeon makes small-size incisions in the body of the patient, into which he inserts trocars intended for passage of instruments and display apparatus, such as an endoscope or a laparoscope to better observe the intervention zone. The trocars which permits passage of display apparatus are called “optical trocars” and generally have inner diameters of 10 mm or 12 mm. Trocars which allow passage of surgical instruments are called “operating trocars” and generally have inner diameters of 5 mm, given that operating trocars of inner diameter of 8 mm, 10 mm or 12 mm can also be used if the operation requires them.
Due to the advantages of this surgical technique for the patient, especially in terms of patient comfort, rapid postoperative recovery, and short hospitalisation, numerous tools have been developed to allow the surgeon to make gestures as precise as those made in open surgery where he benefits from wider access to the intervention region. But tools proposed to date still have drawbacks which hamper progress of minimally invasive surgery. Of these problems, the lack of dexterity or minimal mobility offered by current tools have been cited by doctors.
Robotic tools with internal mobilities, that is, having different degrees of freedom actuatable inside the body of the patient, exist today in a clinical routine (instruments of the DaVinci robot) or in the form of a research laboratory prototype. For insertion of these tools via conventional operative trocars, actuation of internal mobilities of these tools is done by way of remote means (for example, cables, links, tension wires, springs and belts, pulled by actuators placed on the proximal part of the instrument). These actuation devices result in substantial bulk outside the patient, around the surgeon.
Another solution consists of executing the internal mobilities by using direct actuations (that is, mini-motors placed in the distal part of the instrument). For technological reasons (size/power of motors compromise), the resulting tool is very bulky and cannot pass through conventional operative trocars. The use of trocars of greater diameter becomes necessary, which cancels out the minimally invasive and non-traumatising character of the surgical procedure. Also, modularity in design of a tool or medical system has been taken into account in a number of works.
For example, U.S. Pat. No. 6,074,408 refers to a disassemblable modular medical instrument to allow for easier cleaning and replacement of faulty components. Its actuation is based on control by internal cable. The document WO 98/49 951 as such describes a modular surgical instrument allowing interchangeability of the tool due to a ratchet and pawl system. U.S. Pat. No. 7,150,751 refers to the design of a connector for a modular tool.
However, these systems, although modular, have been designed for an assembly external to the body of the patient. In fact, the tool is first fully assembled and then introduced into the body of the patient to carry out the task for which it was designed. This supposes either the use of trocars of considerable diameter for passage of these tools, with harmful consequences to postoperative follow-up, or the design of small-footprint tools which can pass through trocars of lesser diameter, though to the detriment of degrees of freedom.
A number of works has proposed original architectures for medical tools such as endoscopes or other surgical tools, where memory-form alloys are sometimes used, in the ongoing attempt to improve dexterity of the doctor as he carries out surgical gestures. An orientation device with three degrees of freedom and actuated by cables is the subject matter of U.S. Pat. No. 6,685,698.
The article by T. Takayama, T. Omata, T. Futami, H. Akamatsu, T. Ohya, K. Kojima, K. Takase and N. Tanaka (“Detachable-fingered hands for manipulation of large internal organs in laparoscopic surgery”, Proc. of International Conference on Robotics and Automation (ICRA), pp. 244-249, 2007), describes as such the assembly, inside the abdomen, of mechanical fingers constituting a “hand”, the function of which is to grip, manipulate or push large internal organs. However, in this device, the number of fingers is restricted to three. Also, their actuation is done mechanically by cables, by manual action of the surgeon exerted on the proximal part of the instrument. It is understood that the number of degrees of freedom generally presented by existing instruments for minimally invasive surgery is too low, and that their actuation by cables results in substantial bulk outside the patient.
A first aim of the invention is to design a modular tool with internal mobilities—that is, which can give the surgeon all the degrees of freedom he needs—and which at the same time can be easily assembled and disassembled. Another aim of the invention is to provide a modular tool of sufficiently small dimensions so that it can be inserted into the human body via an opening of minimal diameter, to limit postoperative consequences for the patient. Another aim of the invention is to allow use of a non-remote power source to prevent actuation by cables causing considerable mechanical stress. Finally, the modular tool should be able to be adapted for use in a robotic system.